Motion apparatus with improved motion space

ABSTRACT

A motion simulator, comprising a platform carried by at least three pairs of length-adjustable legs, wherein the connection between each leg and the platform comprises a first coupling, wherein the distance between the first coupling of one pair of legs is smaller than the distance between the first coupling of different pairs, wherein, viewed in the top plan view, at least two first couplings are located on a first circle and at least two further first couplings on a second circle, wherein the first and the second circle are concentric and have a different radius.

[0001] The invention relates to a motion apparatus. In particular, the invention relates to a motion apparatus provided with six length-adjustable legs. Such a motion apparatus is known as Stewart platform and is, for example, described by D. Stewart, “A platform with six degrees of freedom”, The institution of mechanical engineers, Proceedings 1965-66, volume 180, part 1, number 15.

[0002] In the known Stewart platform, six legs of equal length and equal adjustability are used, which are connected by first, upper couplings to the platform and by second, lower couplings to a base plate. The legs are arranged in three pair, while, of each pair, the first couplings are arranged closely together, forming three pairs of fit couplings, which pairs are evenly distributed over an imaginary circle. The second couplings of two legs ling side by side of two pairs lying side by side are, each time, relatively close to each other, forming, again three pairs of couplings, which are also evenly distributed over an imaginary circle. Thus, a symmetrical motion platform is obtained, the centre of the platform having a symmetrical motion envelope. This means that in the motion envelope, no main direction of movement can be indicated.

[0003] It has already been suggested to place the first and/or second couplings on an imaginary ellipse (Sunjoo K. Advani). The angle, included between the different pairs of first and second couplings, respectively, can then be chosen to be different than 120°. Thus, already, a more advantageous motion envelope is obtained

[0004] It has been found that with these known motion apparatuses no optimal motion envelope is obtained. This is, inter alia, limited by the length and adjustability of the legs, but also because there is the risk of the legs coming into contact with each other and/or the platform.

[0005] The invention has for its object to provide a motion apparatus of the type described in the opening paragraph, wherein the drawbacks mentioned are obviated while maintaining its advantages. To that end, a motion apparatus according to the invention is characterized by the features of claim 1.

[0006] In a motion apparatus according to the present invention, at least the first couplings of three pairs of legs are arranged pair-wise, such that at least two first couplings are located on a first circle, at least two first couplings on a second circle, concentric with the first circle, which circles are not identical to each other. Preferably, two first couplings, in particular a first pair of first couplings, are on the first circle, the other first couplings on the second circle.

[0007] Herein, the circles and ellipses, to be discussed later, are understood to be viewed in top plan view of the motion apparatus during use, with the platform substantially horizontal, at least in a middle position.

[0008] By arranging the first couplings on two different, concentric circles, the advantage is achieved that a motion apparatus is obtained having a motion envelope, i.e., adjustment range, which is particularly well suited to a desired, possible motion pattern for simulating all sorts of different vehicles, such as airplanes, cars and the like. In particular, thus, legs are prevented from coming into contact with each other and the platform before desired limits of the motion envelope have been reached. Moreover, thus, the dexterity is minimized.

[0009] In further elaboration, the first couplings are located on two ellipses, which ellipses preferably have major axes intersecting at a substantially right angle, while, preferably, the major axis of one of the ellipses extends between two first couplings of one pair of legs. Thus, the advantage is achieved that the legs can move one along the other relatively easily, in particular also at movements of the platform approximately along the major axis of one of the two ellipses, in particular along the major axis of that ellipse which extends between the coupling elements of the pair mentioned.

[0010] In an alternative embodiment, two first couplings are located on the first circle, in particular one pair, while, each time, a first coupling of the further two pairs of first couplings is located on the second circle, and the second first couplings of the respective pairs are located on a first and second line, respectively, which extends through the other first coupling of the respective pair of first couplings, which first or second line, respectively, includes an angle with the tangent at the location at the second circle. Through a suitable combination of, on the one hand, an angle between a line from the centre of the concentric circles at the middle between the first couplings of the pairs whose first coupling is located on the second circle and a line through the first couplings located on the second circle, and on the other hand, the angle included between said tangent and the first and second line, respectively, a still further improved, at least adapted motion envelope can be obtained. The angles mentioned can simply be chosen on the basis of the desired motion envelopes.

[0011] The first couplings can all be located in one plane, but are preferably located in different planes, while, also within first pairs of couplings, the first couplings can be moved in vertical and/or horizontal direction relative to each other. Thus, in an even simpler manner, legs are prevented from coming into contact with each other before the desired limits of the motion envelope have been reached.

[0012] In addition to the afore-described positioning of the first couplings, a similar or comparable positioning of second couplings for the bottom ends of the legs on the base plate can be chosen. The second couplings also can be located on at least concentric circles and/or ellipses, comparable to the first couplings. The second coupling are then located on at least a third and fourth circle, which circles are concentric and preferably approximately equal to or larger than the first and/or second circles.

[0013] In a motion apparatus according to the present invention, the lengths of the legs and/or adjustment ranges can be selected to be different, while, with each leg in a middle position, the centre of the platform (the geographic centre between the six first couplings, to be indicated, viewed in top plan view, as kinematic centroid) can be moved relative to the geographic centre between the second couplings. Also, the centre of the concentric first and second circles can, in top plan view, be moved relative to the centre of the concentric third and fourth circles. Thus, an adjustment range of a platform can be even further optimized. When manufacturing a motion apparatus according to the present invention, on the basis of an analysis of motions (in normal and extreme cases) of a vehicle to be simulated, such as a plane, car or the like, leg lengths can be determined, preferably experimentally or by computer simulations, while, moreover, suitable platform sizes are determined. On the basis thereof, a desired optimal motion envelope is determined, whereupon, for each of the first couplings and second couplings the optimal location is calculated with the aid of a computer and simulation program, while each leg is optimized in length and adjustment range. In such a manner, for each vehicle an optimal motion apparatus can be obtained, while legs are prevented from moving against each other in each others motion envelopes before limits of the necessary motion envelopes are reached.

[0014] In a particularly simple embodiment, couplings are provided such as ball and socket joints, at least cardan hinges (gimbals), while, each time, a pair of couplings is included in a joint housing. The ball and socket joints are adjustable within the housing in a simple manner, so that the location of the respective couplings in the pair can be adjusted in a simple manner. To that end, for instance filler blocks, suitable clamping means, screw means or the like can be used.

[0015] In a further advantageous embodiment, the position of one or more couplings (gimbals) is adjustable relative to one or more further couplings in the same or a different pair. Preferably, setting is also possible during use. Herewith, actively, the or each motion envelope of the motion apparatus can be set and adjusted, while the centre can be moved.

[0016] Herein, a motion apparatus is understood to include at least a movement simulator, a robot platform, a motion apparatus for use in telerobotic surgery and the like.

[0017] In the subclaims, further advantageous embodiments of a motion apparatus according to the invention are represented. In explanation, exemplary embodiments of a motion apparatus in the form of a motion simulator according to the invention will be further elucidated with reference to the drawing. In the drawing:

[0018]FIG. 1 schematically shows, in side view, a motion simulator according to the present invention;

[0019]FIG. 2 shows, in top plan view, a first arrangement of first and/or second couplings of a motion simulation according to FIG. 1;

[0020]FIG. 3 schematically shows, the arrangement of first and/or second couplings in a first alternative embodiment;

[0021]FIG. 4 shows an arrangement of first and/or second couplings in a second alternative embodiment; and

[0022]FIG. 5 shows a graph of a motion envelope obtained with a motion simulator according to the present invention, wherein the three Euler angles psi, theta and phi are shown of yaw, pitch and roll of the platform, respectively, relatively to the axis system of the fixed world.

[0023] In this description, identical or corresponding parts have identical or corresponding reference numerals. In this drawing, in FIGS. 2-4, the location is indicated of first coupling means on a first and second circle and on a first and second ellipse. As to the second coupling means, the bottom ends of the legs, the same drawings can be given, wherein, however, the first circle is replaced by a third circle, preferably approximately identical to or larger than the first circle, and the second circle is replaced by a fourth circle, approximately as large as or larger than the second circle. The position of the three pairs of second couplings will then, for instance, be mirrored along the line K extending in the drawing horizontally through the centre M of the circles. However, the included angles may be different For simplicity's sake, by way of illustration, only in FIG. 2 such a third and fourth circle have been drawn. Naturally, in the same or a comparable manner third and fourth circles can be provided in the further embodiments. The second couplings can, for that matter, also be situated on one (third) circle. The legs can have the same or different lengths.

[0024] In FIG. 1, in schematic side view, a simulator 1 according to the invention is shown, comprising a base plate 2, a platform 3 and a series of legs 4, three of which have been drawn. The legs 4 are shown as drawn, straight lines, yet it will be clear that they are length-adjustable, for instance hydraulically, electromechanically or pneumatically, or have adjustable piston cylinder assemblies or screw spindles or the like. Such length-adjustable legs are known per se from practice, for instance from the Stewart platform mentioned. The legs 4 are connected to the platform 3 in six first couplings C1-C6, while the bottom ends are connected to the base plate 2 by second couplings G1-G6. As is apparent from FIG. 1, the different couplings C1-C6, G1-G6 are at different levels N1-N6, measured above or under the base plate 2 with the platform in a middle position, for instance a horizontal position as shown in FIG. 1. The middle position is for instance determined by adjusting all legs 4 at an average length.

[0025] In FIGS. 2-4, the positions of the first and/or second couplings C1-C6, G1-G6 are shown, in top plan view, i.e. at right angles to the base plate 2 with the platform 3 in the middle position. It will be clear that in the middle position, the platform 3 can also be inclined, for instance in that the edge of the platform shown in FIG. 1 at the left hand side is lower than the one at the right hand side, for instance because the desired motion envelope demands this. The “platform” for that matter can also be formed differently, for instance as a dish part which is located partly under the plane formed by at least three first couplings.

[0026] In FIG. 2, a first position is shown of the first couplings C1 -C6 and the second couplings G1-G6. The first couplings C1, C2 form a first pair 5 of first couplings, the couplings C3 and C4 a second pair 6 of first couplings and the first couplings C5 and C6 a third pair 7 of first couplings. The second couplings G1 and G2 form a first pair 8 of second couplings, the second couplings G3 and G4 form a second pair 9 of second couplings and the couplings G5 and G6 a third pair 10 of second couplings. The first pair 5 and second pair 6 of first couplings are located on a first circle 11, the third pair 7 on a second circle 12. The first and second circle 11, 12 are concentric with a centre M between the pairs 5-7 mentioned. The first circle 11 has a first radius R₁, the second circle 12 a smaller, second radius R₂. Through the third pair 7 of first couplings C5, C6 and the centre M of the circles 11, 12, a first line L₁ extends, through the centre M, at right angles to the first line L₁, a second line K. From the centre M, two second lines L₂ each extend at an angle α relative to the line K through the centre of the first and second pair, 5, 6, respectively, of first couplings C1, C2 and C3, C4, respectively. The angle α can for instance be 30°, so that between the first and the second line L₁, L₂, each time, 120° is included, yet also a different, smaller or larger angle can be involved.

[0027] Further, in FIG. 2, a third circle 13 and, concentric therewith, a fourth circle 14 have been drawn, which have a centre M₂ which is off-set relatively to the centre M of the first and second circle. On the fourth circle, the third pair 10 of second couplings G5, G6 is located, on each side of a third line L₃ one second coupling G5, G6. The third line L₃ extends parallel to the first line L₁, through the centre M₂. Each time, a second coupling G1 and G4, respectively, of the first and second pair 8, 9 of second couplings is located on the third circle 13. Moreover, the first pair 8 is on a straight line V₃, which includes an angle γ with a tangent T at the third circle 13 at the location of the second coupling G₁ located on the third circle. In a similar manner, the second couplings G₃ and G₄ lie on a straight line V₄, which also includes an angleγ with a tangent at the circle 13 at the location of coupling G₄. In this embodiment, the second couplings G₂, G₃are outside the third circle 13, but they could also lie inside it. Due to a suitable angle γ, the legs 4, connected to the first and second pairs 8, 9 of second couplings, respectively, are prevented from coming into contact with each other upon movement of the platform.

[0028] It will be clear that the centres M and M2 can also coincide, at least can be off-set relatively to each other in the plane of the drawing or in a different manner.

[0029]FIG. 3 shows an alternative embodiment, wherein only first couplings C1-C6 are shown. In this embodiment, a first and second pair 5, 6 of first couplings C1, C2 and C3, C4, respectively, are located on a relatively large, second ellipse E2, while the third pair 7 of first couplings C5, C6 is located on a first ellipse E1. The first ellipse E1 has a major axis L1 which extends through a centre M and between the first couplings C5, C6. The second ellipse has a major axis K which extends at right angles to the major axis L1 of the first ellipse E1, parallel to the minor axis K1 thereof. The minor axis K1 of the first ellipse E1 is at a distance D from the major axis K of the second ellipse E2. The first and second pair 5, 6 is adjusted at an angle α to the major axis K, at the side thereof remote from the third pair C5 C6. The first couplings C1, C4 are then on a first, largest circle 13, the first couplings C2, C5, C6 and C3 on a smaller second circle 14. The first and second circle 13, 14 have only been partly drawn and are located concentrically with a centre M3 above the centres M, M2 of the first and second ellipse E1, E2. Subsequently, FIG. 4 shows a third embodiment wherein each time a first coupling C1, C4, respectively, of a first pair 5 and a second pair 6 of first couplings is located on a circle 13, while the third pair 7 of first couplings C5, C6 is located on the smaller circle 14, concentric therewith. The first couplings C1 and C2 of the first pair 5 are located on a straight line V1, which includes an angle γ with a line L2 through the respective first coupling C1 of the respective pair located on the first circle and the line L2 extending through the centre M. The line L2 includes an angle α with the line K through the centre M, at right angles to the line L1 through the centre and the third pair 7. The advantages of such an arrangement have already been discussed in relation to the second couplings G1-G4 of FIG. 2.

[0030] In FIG. 5, an envelope is drawn of a motion simulator 1 according to the invention, wherein the motion envelope B is indicated with squares W which define an outer surface of the motion envelope B and, at least for the greater part, enclose a cube Z. The cube Z is drawn in and indicates the cube-shaped target function which ideally, should be enclosed by the motion envelope (workspace). In this drawing, the angles of the cube Z indicate a specific prerequisite for approximately 18° pitch, 15° roll and 20° yaw, which occur simultaneously in conformity with the standard Euler angles psi, theta and phi of yaw, pitch and roll, respectively, of the platform relatively the fixed world. It be clear that in the same or comparable manner for other angles for pitch, roll and yaw, comparable cubes Z with motion envelopes B can be determined. On the other hand, starting from predetermined real or theoretic values for the desired angles for roll pitch and yaw, each time, a workspace can be determined on the basis of which it can be calculated in what manner the location of the different first and second couplings C1-C6, G1-G6 and the length and adjustability of the different legs 4 is to be determined.

[0031] As is clearly shown in FIG. 1, the first couplings C and second couplings G are located at different levels N, to which end the couplings, designed as ball and socket joints, are each time included, pair-wise, in housings 20, in which housings the pairs 5, 6, 7 of first couplings C1, C2; C3, C4; C5, C6 or pairs 8, 9, 10 of second couplings G1, G2; G3, G4; G5, G6 are received. Preferably, each time, the housings 20 are identical and designed in a manner known per so, while, nonetheless, means are provided for adjusting at least one of the couplings C, G, respectively, received within the respective housing, relative to the other coupling C, G, respectively, received therein. In this manner, a particularly simple construction is obtained while a large freedom for setting is achieved.

[0032] It is advantageous if one or more couplings C, G is movably arranged. For instance, in FIG. 1, the coupling C1 at the platform 3 and the coupling G5 on the base 2 are settable for height with the aid of a suitable adjustment mechanism 20, for instance a screw spindle or a piston cylinder assembly. Herewith, the position of the respective coupling C, G, relative to the platform 3 and the basis 2, respectively, can be adjusted, preferably actively, during use of the platform as well as in between two situations of use. Both individual couplings and pairs of couplings can be adjustable, for instance by moving the housings. Due to such adjustability, a motion apparatus can be adjusted to a new simulation environment rapidly and in a simple manner, for instance to a different vehicle to be simulated or a different situation of use, for instance from the approach of an airplane to taxiing after landing. When used as robot platform, adjustment in a rapid and simple manner to a new condition of use, for instance a different product to be processed or a different operation is possible.

[0033] The invention is not limited in any manner to the exemplary embodiments represented in the drawing. Many variations thereon are possible within the framework of the invention outlined by the claims.

[0034] For instance, differently shaped platforms 3 and/or base plates 2 can be used within the invention, while all sorts of other couplings can be used. The cube Z aimed at for, for instance, rotations, can also be orientated in space differently, while the surrounding envelope B can be moved along by adjusting the position of the first couplings C, the second couplings G and/or the length and/or the adjustability of the legs 4, Precisely because not all first couplings C and second couplings G are located on a circle or ellipse, a larger adjustment range, at least a better fitting envelope B is obtained, so that a better simulation is possible. Moreover, as a result, the legs ran be arranged such that particularly high accelerations are possible and/or relatively low forces can occur.

[0035] These and many comparable variations are understood to fall within the scope of the invention outlined by the claims. 

1. A motion simulator, comprising a platform carried by at least three pairs of length adjustable legs, wherein the connection between each leg and the platform comprises a first coupling, wherein the distance between the first couplings of one pair of legs is smaller than the distance between the first coupling of different pairs, wherein, viewed in top plan view, at least two first couplings are located on a fist circle and at least two further first couplings on a second circle, wherein the first and the second circle are concentric and have a different radius.
 2. A motion simulator according to claim 1, wherein the legs are connected to a base plate via second couplings, such that, each time, the second coupling of one leg of one pair is located closer to a second coupling of another pair than to the second coupling of the other leg of the respective pair, wherein, viewed in top plan view, at least two second coupling are located on a third circle and at least two further second couplings on a fourth circle, wherein the third and fourth circle are concentric and have a different radius.
 3. A motion simulator according to claim 1 or 2, wherein the first couplings of two pairs of legs are located on a first circle and the first couplings of a third pair on the second circle.
 4. A motion simulator according to claim 1 or 2, wherein the first couplings of a first pair of legs and two first couplings of two other pairs or legs are located on a first circle and the two further first couplings of the respective two other pairs of legs are located on the second circle.
 5. A motion simulator according to claim 4, wherein the first couplings of the first pair of legs are located on a first ellipse and the first couplings of the two further pairs of legs are located on a second ellipse.
 6. A motion simulator according to claim 5, wherein the first ellipse has a major axis which extends approximately at right angles to a connecting line between the first couplings of the first pair of legs, wherein the second ellipse has a major axis extending approximately at right angle to the major axis of the first ellipse and wherein the two major axes intersect off-centre.
 7. A motion simulator according to claim 6, wherein the major axis of the first ellipse has a length which is approximately equal to the length of the minor axis of the second ellipse.
 8. A motion simulator according to any one of the preceding claims, wherein the first couplings of a first pair of legs are located on the second circle, wherein the first couplings of two further pairs of legs are located on a first and a second line, respectively, wherein, of each further pair a first coupling is located on the first circle and wherein the first and second line include an angle with a tangent at the first circle in the respective first coupling located thereon.
 9. A motion simulator according to any one of the preceding claims, wherein different first couplings are located at different heights with a platform extending approximately horizontally.
 10. A motion simulator according to any one of claims 2-9, wherein the second couplings of two pairs of legs are located on the third circle and the second couplings of a third pair on the fourth circle.
 11. A motion simulator according to claim 10, wherein the second couplings of a first pair of legs and two second couplings of two other pairs of legs are located on the third circle and the two further second couplings of the respective two other pairs of legs are located on the fourth circle.
 12. A motion simulator according to claim 11, wherein the second couplings of the first pair of legs are located on a third ellipse and the second couplings of the two further pairs of legs are located on a fourth ellipse.
 13. A motion simulator according to claim 12, wherein the third ellipse has a major axis which extends approximately at right angles to a connecting line between the second couplings of the first pair of legs, wherein the fourth ellipse has a major axis which extends approximately at right angles to the major axis of the third ellipse and wherein the two major axes intersect off-centre.
 14. A motion simulator according to claim 13, wherein the major axis of the third ellipse has a length which is approximately equal to the length of the minor axis of the fourth ellipse.
 15. A motion simulator according to any one of claims 10-14, wherein the second couplings of a first pair of legs are located on the fourth circle, wherein the second couplings of two further pairs of legs are located on a third and fourth line, respectively, wherein a second coupling of each further pair is located on the third circle and wherein the third and fourth line include an angle with a tangent on the third circle in the respective second coupling located thereon.
 16. A motion simulator according to any one of claims 10-15, wherein different second couplings are located at different heights relative to the base plate.
 17. A motion simulator according to any one of the preceding claims, wherein two first or second couplings are included in one joint holder, wherein the mutual distance is adjustable in at least one direction, in particular in a direction approximately at right angles to the platform and the base plate, respectively.
 18. A motion simulator according to any one of the preceding claims, wherein the length and adjustability of the legs is chosen such that the centre of the platform, at least a specific location on the platform, has a specified motion envelope, which, at least insofar as rotation envelopes are concerned, is preferably somewhat block-shaped. 